Solar battery panels are used under outdoor environment where the temperature fluctuates severely. Therefore, in order to enhance the thermal stability, the solar battery assembly after forming is subjected to a long-time heat treatment (a curing process). As a device for a curing process, a multistage stocker type curing oven device as described in Japanese Patent Provisional Publication No. HEI 11-238898A is known. By using such a multistage stocker type curing oven device, it becomes possible to subject a plurality of solar battery assemblies to the curing process simultaneously, and to effectively perform the curing process which requires a long time.